With the kevlar shock cord it's a good idea to toughen up the end of the body tube where the cord passes over it. One way is to make up a little epoxy and with a glove on (Latex or whatever you use) rub it into the cardboard to make it more resistant to cutting. Medium CA also works good for this. A wrap of some kind of plastic tape on the cord where it passes through the end is also a good idea. It spreads the load.
All of this is to help with NOT learning another new skill, the repair of the Dreaded Zipper
Thanks for the tip Dave, I've been re-enforcing my LPR birds with CA and plan on doing the same with this one. I am also going to wind some tape around the cord where it rubs on the body tube as you suggested.
cheers - mark